POUL LARSEN 



and 

 TORBJ0RN AASHEIM 



University of Bergen 



Tke Occurrence of lndoie-3-aceialdehyde in 



Certain Plant Extracts 



In 1939 (19) the senior writer detected a neutral growth substance in 

 extracts of etiolated epicotyls of Pisiim sativum and Vicia faba and 

 in hypocotyls of Helianthus. Subsequent investigations of this sub- 

 stance (20, 21) led to the conclusion that it was identical with indole- 

 3-acetaldehyde (lAAld) . Since the active material was not isolated in 

 the chemically pure state, its identification rested on indirect evidence. 

 Similar evidence for the occurrence of lAAld in extracts of other plants 

 was subsequently provided by Hemberg in 1947 (16), Gordon and 

 Sanchez Nieva in 1949 (11, 12), Yamaki and Nakamura (31), and 

 others. The literature concerning the occurrence and possible function 

 of lAAld in plants has been reviewed by Larsen, 1951 (22) , and Gor- 

 don, 1954 (8) . Among the more recent studies of these problems may 

 be mentioned the ones by Wiedow-Patzold, 1955 (30) , Gordon, 1956 

 (9, 10), and Clarke and Mann, 1957 (7). 



The only other natural auxin that had been claimed to play a role 

 in plant growth regulation was Kogl's auxin a lactone. As it became 

 more and more unlikely that this compound (or auxin a or b) oc- 

 curred in plants, it became customary to ascribe auxin activity found 

 in nonacidic fractions of plant extracts to the action of lAAld. In 

 1952, however, lAAld was synthesized by Brown, Henbest, and Jones 

 (6) , and in the same year, indole-3-acetonitrile (IAN) was isolated 

 from cabbage in the chemically pure state by Jones, Henbest, Smith, 

 and Bentley (18). The biological activities of the two neutral syn- 

 thetic auxins were studied by Bentley and Housley (4) and by Bentley 

 and Bickle (3) . 



Two neutral auxins had now to be considered, and since the occur- 

 rence in plants of the lAAld still rested on indirect evidence only, it 

 was natural for some workers to suspect that in the past the aldehyde 



[43] 



